An increasingly large number of cases of patients with an acquired deficiency in cell mediated immunity complicated by opportunistic infections(OI) and Kaposi's sarcoma (KS) are being seen among homosexual males, drug addicts, otherwise normal heterosexual Haitians and a small number of individuals who have received blood products. The mortality rate may be as high as 40% in 1 year and 80% in 2 years. This ongoing outbreak represents a new clinical entity of unknown etiology. Working under the hypothesis that the disease may result from an infectious agent that induces immunosuppression, we will look for the presence of such an agent in the blood mononuclear cells of patients. We will attempt to determine by tests in vitro if the low number of helper-inducer T lymphocytes alone can explain the immunological abnormalities, or whether the lymphocytes also are functionally abnormal on a per cell basis. By a comparison of immunological tests in addict and homosexual patients we will attempt to determine if these two groups have the same underlying syndrome. We will examine the immunological response to cytomegalovirus in order to determine if differences exist between patients who acquire KS and those who do not. 40ml. of blood will be drawn from normal subjects and from patients. A superficial 3mm. skin biopsy will be obtained from 12 volunteer patients.